code: def test_retain_period_common_to_all(self):
      seriesA = TimeSeries.from_times_and_values(
          pd.date_range("20000101", "20000110"), range(10)
      )
      seriesB = TimeSeries.from_times_and_values(
          pd.date_range("20000103", "20000108"), range(6)
      )
      seriesC = TimeSeries.from_times_and_values(
          pd.date_range("20000104", "20000112"), range(9)
      )
      seriesC = seriesC.stack(seriesC)
  
      common_series_list = retain_period_common_to_all(
          [seriesA, seriesB, seriesC]
      )
  
      # test start and end dates
      for common_series in common_series_list:
          assert common_series.start_time() == pd.Timestamp("20000104")
          assert common_series.end_time() == pd.Timestamp("20000108")
  
      # test widths
      assert common_series_list[0].width == 1
      assert common_series_list[1].width == 1
      assert common_series_list[2].width == 2
  
file_path: darts/darts/tests/utils/test_utils.py
imports: import numpy
  import pandas
  import pytest
  from darts import TimeSeries
  from darts.utils import _with_sanity_checks, retain_period_common_to_all
  from darts.utils.missing_values import extract_subseries
label_desc: Use image node_id 1 for calling the TestUtils obj's underlying member method code with example usage: obj.test_retain_period_common_to_all() without return types